1. Field of the Invention
The invention pertains generally to the field of guided wave optical communication systems and more particularly relates to low loss optical-data single fiber switching devices for performing multi-mode or single-mode access coupling in data distribution networks, as well as multiplexing and demultiplexing functions in electro-optical data processing apparatus.
2. Description of the Prior Art
In the R. A. Soref U.S. patent application Ser. No. 856,424 now U.S. Pat. No. 4,143,941, for a "Low Loss Optical Data Terminal Device for Multimode Fiber Guide Optical Communication System," filed Dec. 1, 1977 and assigned to Sperry Rand Corporation, issued Mar. 13, 1979 as U.S. Pat. No. 4,143,941 it is observed that considerable past research has been directed to the fiber optic bundle and to single mode integrated techniques for use in optical data communication, but that more recent interest has turned to the alternative of the multi-mode, single optical fiber technology. The latter can be successfully applied to a wide variety of communication problems, especially where moderate band width and moderate distances are involved. Fabrication of passive interconnectors is simplified and the packing fraction losses characteristic of the fiber bundle method are eliminated. Although significant progress has been made in the single mode technology, important unsolved coupling problems are seen to remain.
Simple light sources exist easily capable of coupling considerable power into available multiple mode, single fiber guides, and adequate photodetector devices for detecting the flow of light through such single fiber guides are also available. Evidently, a scheme for multiple mode, single fiber communication would be made useful if adequate concepts existed for electrically controlling the routing of optical signals, so that data bussing, multiplexing, demultiplexing, and switching functions could be performed totally in the optical domain by reliable and inexpensive devices.
In the Soref patent application, there is described just such an active reciprocal optical device finding utility in optical processing, for example. It includes a lineal array of multiple mode optical fiber input-output guides abutted against a flat input-output focal face of an electrooptically active plate provided with appropriate deflection modulation electrodes on each of its two broad faces perpendicular to the plane of the focal face. Opposite that input-output face is a curved mirror surface for refocussing TE and TM multi-mode light from a predetermined input fiber guide into a second one of the array of fiber guides as selected by the voltage applied to cooperating sets of essentially symmetric angular electrodes.